Air filter unit

ABSTRACT

An air filter unit for removing contaminations from air is disclosed. The air filter unit includes an airflow generating device configured to generate and direct at least one airflow from an air inlet to an air outlet, a filter disposed between the air inlet and the air outlet and including at least one filter layer for removing contaminations from the at least one airflow, a heater disposed upstream of the filter and configured to heat the at least one airflow directed towards the filter, an ejection device disposed upstream of the filter and configured to inject a sterilizing agent into the at least one airflow directed towards the filter, and a duct interposed between the air inlet and the filter and configured to feed the at least one airflow to the filter. The duct includes a volute-like outlet portion, and the ejection device is arranged in the duct.

The present invention relates to an air filter unit for removingcontaminations from an airflow directed into a clean/sterileenvironment, such as an aseptic working environment

Filter units are generally used for cleaning air from macroscopic andmicroscopic contaminations such as dust, microbes and viruses. Anairflow is directed through the filter unit in such a way that undesiredcontaminations are retained by the filter unit and sterile aircontaining a reduced number of contaminations or no contaminations atall exits the filter unit and is directed into clean/aspetic/sterileworking environment or a clean room requiring sterile air.

Filter units for supplying strile air to sterile working environmentsare commonly used in medical facilities or in automotive, electronic,pharmaceutical and biotechnology industries or even in the foodpackaging industry, lust to name a few.

Filter units exist in a large variety of solutions and new developmentsare ongoing in order to improve the quality of the filter unitsthemselves, and, accordingly, to improve the quality and the sterilityof the air exiting the filter units.

Filter units are known which comprise one single High-EfficiencyParticulate it (HEPA) filter layer or one single Ultra-Low ParticulateAir (ULPA) filter layer. These solutions are commonly used for the moststringent applications, including e.g. applications in the foodpackaging industry, in particular for allowing aseptic productionconditions, where sterile working environments are required to increaseshelf-life stability of the packaged product and, consequently, consumersafety.

Recently, filter units comprising at least two filter layers have beendeveloped to increase filter efficiency and to guarantee that, even inthe event of damage of one filter layer, the air entering theclean/sterile working environment is sterile. This is now one of therequirements laid down by FDA for sterile working environments in thefood industry.

It has to be considered that from time to time the filter units need tobe sterilized themselves in order to devitalize contaminants such asmicrobes, viruses and spores filtered out of the air by the filterlayers and trapped in these filter layers so that the required qualityof the filter units and their respective filter efficiencies can bere-established. Therefore, the design of filter units also needs toconsider adequate and efficient means and ways of sterilization.

An example of a known air filter unit comprising respectivesterilization means is described in EP2049227. This filter unitcomprises a blower configured to direct an airflow, heated by anintegrated heating device, through two filter layers; the filter unitfurther comprises a sterilization layer, which is interposed between thetwo filter layers and in which liquid or vaporous hydrogen peroxide(H₂O₂) can be injected to sterilize the filter unit. A pre-filter isalso provided at an air inlet to filter out larger contaminations fromthe airflow entering the unit. During the sterilization of the filterunit, the two filter layers are saturated with liquid or vaporoushydrogen peroxide injected through the sterilization layer and theheating device and the blower are activated. Thus, an airflow isgenerated through the two filter layers.

The heating device heats the airflow to a temperature above, theactivation temperature of the hydrogen peroxide, so that the hydrogenperoxide degrades and reacts on contaminations such as microbes, virusesand speres. Eventually, the blower and the heating device aredeactivated once the degradation and, thus, the reaction on thecontaminations of the hydrogen peroxide has been initiated. After thesterilization reactions have been terminated, the filter layers can bedried by activating again the blower and the heating device. At the veryend, the blower can be activated to remove the degradation products fromthe filter unit.

Another example of a known air filter unit, in particular for supplyingclean/sterile air to a work environment in a food packing factory, isdisclosed in

This filter unit comprises:

-   -   a blower configured to generate and direct en airflow from an        air inlet to an air outlet;    -   a pre-filter arranged at the air inlet for filtering out        macroscopic contaminations, such as larger diameter dust, from        the airflow entering the filter unit;    -   two filter layers oriented perpendicularly to each other and        through which the airflow coming from the pre-filter passes        prior to enter the clean/sterile working environment;    -   a heater arranged between the blower and the two filters and        adapted to adjust the temperature and the n humidity of the        airflow; and    -   a chemical gas agent eject apparatus configured to inject        gaseous hydrogen peroxide into the airflow upstream of the two        filters and downstream of the heater.

In the example embodiment described in US 2009/169421, the first filterlayer crossed by the airflow includes a HEPA filter, whilst the otherfilter layer includes an ULPA filter,

The operation of the filter unit shown in US 2009/169421 is similar tothat described with reference to the filter unit of EP2049227, Even inthis case, during sterilization, hydrogen peroxide is supplied throughthe chemical gas agent eject apparatus into the airflow, which issimultaneously heated to a given temperature.

Air filter units of the type described above are used widely andsatisfactorily to supply cleaned/sterilized air to clean/sterile workingenvironments. Within the industry, however, of demand for furtherimprovements is felt, particularly in view of the continual request toincrease the filter performance as well as the sterilization efficiencyand reliability of the known air filter units,

It is therefore an object of the present invention to provide an airfilter unit, which allows to satisfy the aforementioned, demandtypically associated with known filter units.

According to the present invention, there is provided an air filter unitas claimed in claim 1.

A preferred, non-limiting embodiment of the present invention will bedescribed by way of example with reference to the accompanying drawings,in which:

FIG. 1 shows a perspective view of an air filter unit according to thepresent invention, with parts removed for clarity;

FIG. 2 shows a larger-scale perspective view, taken from a differentdirection, of a detail of FIG. 1, with parts removed for clarity; and

FIG. 3 shows a larger-scale perspective view, taken from the samedirection as FIG. 2, of another detail of FIG. 1, with parts removed forclarity.

Number 1 in FIG. 1 indicates as a whole an air filter unit adapted toclean air, i.e. to remove contaminants from the air. The unit 1 isadapted to be placed at the boundary between an untreated environment 2and a clean/sterile environment 3 in order to direct sterilized air intothis latter environment.

In particular, unit 1 is adapted to generate and direct at least oneairflow F from a respective air inlet 4, connected to the untreatedenvironment 2, to an air outlet 5, connected to the clean/sterileenvironment 3.

In the example shown, unit 1 is adapted to generate two distinctairflows F, each one directed from a respective air inlet 4 to the samecommon air outlet 5.

With reference to FIGS. 1 to 3, unit 1 comprises:

-   -   a filter assembly 6 arranged between air inlets 4 on one side        and air outlet. 5 on the opposite side;    -   two airflow generating devices 7, preferably disposed upstream        of filter assembly 6 and adapted to generate airflows F from the        respective air inlets 4 to air outlet 5;    -   heating means 8 for heating the airflows F before they pass        through filter assembly 6; and    -   ejection means 9 adapted to inject vaporized, gaseous or liquid        sterilizing agent, in particular hydrogen peroxide, into        airflows F directed towards the filter assembly 6.

With reference to FIG. 1, filter assembly 6 comprises a box-likestructure 10, preferably having a parallelepiped configuration; box-likestructure 10 is delimited, at one end, by air outlet 5, and at itsopposite end, by a wall 11 supporting airflow generating devices 7 Asvisible in FIG. 1, air outlet 5 is positioned at the bottom of box-likestructure 10 and is covered by a grid 12 (only partially visible inFIG. 1) for protection purposes against aggressive chemical sterilizingtreatment of the filter unit 1, whilst wall 11 is positioned at the topof the same structure.

Filter assembly 6 comprises:

-   -   a first filter layer 15 interposed between airflow generating        devices 7 and air outlet 5, and therefore between air inlets 4        on one side and the air outlet 5 on the opposite side;    -   a second filter layer 16 extending parallel to filter layer 15        and interposed between the latter and air outlet 5; and    -   a hollow spacer 17 separating filter layers 15 and 16 so as to        create an air cap therebetween.

Filter layers 15 and 16 are both plate-shaped and extend parallel towall 11.

It is pointed out that hollow spacer 17 may be made thinner than the oneshown in FIG. 1 or even eliminated by putting the filter layers 15 and16 in direct contact with one another. In this way, filter assembly 6may be made more compact in a direction orthogonal to filter layers 15and 16.

Filter assembly 6 also comprises two plate-shaped hollow bodies 18, 19,one (13) formed between wall 11 and filter layer 15, and the other one(19) located downstream of filter layer 16 with respect airflows F anddefining air outlet 5.

Hollow body 18 defines a chamber 20, preferably of parallelepipedconfiguration, open towards filter layer 15 and delimited by wall 11 anda by a plurality of lateral walls 21, four in the example shown,protruding orthogonally from respective sides of the wail 11 itself;hollow body 18 creates an air gap between end wall 11 and filter layer15 and is configured to receive airflows F from air-flow generatingdevices 7.

Hollow body 19 creates another air gap between filter layer 16 and airoutlet 5. According to a possible alternative not shown, hollow body 19may be eliminated in order to make filter assembly 6 more compact in adirection orthogonal to filter layers 15 and 16.

With reference to FIGS. 1 to each air-flow generating device comprises ablower 22 adapted to aspirate air from untreated environment 2 throughrelative air inlet and to blow it to a blower outlet 23 in turnconnected with chamber 20 of filter assembly 6; therefore, blower 22 isconfigured to generate a relative airflow F directed to cross filterassembly 6 and to reach clean/sterile environment 3 through air outlet5.

Conveniently, a prefilter 24 is mounted between each air inlet 4 and therelative blower 22 to remove macroscopic contaminations from the airentering the blower 22 itself.

As shown in FIG. 1, air inlets 4 lie on parallel planes orthogonal tofilter layers 15, 16 and to the plane on which air outlet 5 lies. Bloweroutlet 23 lies on a plane parallel to the one of air outlet 5. In theexample shown, air inlets 4 are vertically oriented, whilst air outlet 5and blower outlet. 23 extend horizontally.

In the preferred embodiment described with reference to the enclosedFigures, air inlets 4, air outlet 5 and blower outlet 23 all haverectangular profiles.

Each blower 22 is connected to filter assembly 6 through a relative duct25. In this way, each duct 25 is surmounted by respective blower 22.

With reference to FIGS. 1 to 3, heating means 8 and ejections means 9are advantageously arranged within each duct 25, and this duct 25comprises at least an outlet portion 26 having a volute-likeconfiguration to increase mixing between the relative airflow F and thesterilizing agent injected within the duct 25 itself by ejection means9.

The use of the volute-like outlet portion 26 for each duct 25 alsopermits a very uniform distribution of the heat to the relative airflow5 and/or the mixture of air and sterilizing agent moving towards filterassembly 6.

According to a possible alternative not shown, heating means 8 may bealso arranged upstream of the relative duct 25 with respect to therelative airflow F, for instance they may be integrated in the relativeblower 22.

According to another possible alternative not shown, each duct 25 may bealso entirely configured like a volute.

In the illustrated example, each duct 25 has an inlet portion 27connecting the relative blower outlet 23 to a relative opening 28 formedin wall 11 of filter assembly; the inlet portion 27 of each duct 25 hasan increasing section passing from the relative blower outlet 23 to therelative opening 28; in addition, each inlet portion 27 preferably hasthe shape of a truncated pyramid and is delimited by four lateral walls30, each having substantially the profile of an isosceles trapezium.

Volute-like outlet portion 26 of each duct extends within chamber 20 anddefines a main outlet opening 31 lying on a plane transversal to filterlayers 15 and 16.

More specifically, main outlet opening 31 of each duct 25 lies on aplane slanted with respect to filter layer 15 and defining with thelatter an acute angle; in this way the airflow F exiting from mainoutlet opening 31 of each duct 25 has a given inclination with respectto filter layer 15 smaller than 90° and includes a tangential componentwith respect to the filter layer 15 itself,

Outlet portions 26 of ducts 25 are arranged inside chamber 20 of hollowbody 18 at opposite corners or sides thereof; more specifically, theoutlet portions 26 of ducts 25 are mounted in the proximity ofdiagonally opposite respective corners of hollow body 18.

Outlet portion 26 of each duct 25 is delimited by a curved wail 32,having an arc-shaped lateral profile and facing one of the lateral walls21 of hollow body 18, and by two parallel lateral walls 33 extending onthe opposite sides of curved wall 32; lateral walls 33 and curved wall32 extend on the prolongation of respective lateral walls 30 of therelative inlet portion 27.

In the example shown, curved walls 32 of ducts 25 face opposite lateralwalls 21 of hollow body 18.

Main outlet opening 31 of each duct 25 is delimited by wall 11 and bythe head edges of the relative curved wall 32 and lateral walls 33.

In order Increase turbulence of the air in chamber 20 and therefore abetter heating and mixing of the air with the sterilizing agent prior tosupplying the resulting mixture to filter layers 15 and 15, main outletopenings 31 of ducts 25 face respective staggered portions of anintermediate plane P extending between the ducts 25 themselves andorthogonal to wall 11 and filter layers 15 and 16.

Main outlet openings 31 of ducts 25 lie on respective slanted planesdiverging from one another towards filter layers 15 and 16.

With reference to FIGS. 1 and 2, outlet portion 26 of each duct 25further comprises an auxiliary outlet opening 35 formed in relativecurved wall 32 and disposed opposite to the relative main outlet opening31. Auxiliary outlet openings 35 allow parts of respective airflows F toreach corner areas of filter layers 15 and 16.

In the example shown, each auxiliary outlet opening 35 presents asmaller dimension than the respective main outlet opening 31.

With reference to FIGS. 2 and 3, heating means 8 comprise, for eachairflow F, a serpentine heating member 36 projecting transversallywithin inlet portion 27 of the relative duct 25 from a lateral wall 30thereof and adapted to heat the air coming from the relative blower 22prior to reaching filter layers 15 and 16.

In particular, heating member 36 includes an electric resistance (knowas such and not shown) and is inclined towards outlet portion 26 of therelative duct 25 and therefore towards filter layers 15 and. 16.

This arrangement of heating member 36 within the relative duct 25 isaimed at achieving an uniform. heating of the relative airflow F.

With reference to FIGS. 2 and 3, ejection means 9 comprise, for eachairflow F, an ejection conduit 38 projecting transversally within inletportion 27 of the relative duct 25 from a lateral wall 30 thereof andprovided with at least one radial outlet hole 39 having an axistransversal to the relative airflow F. In the example shown, eachejection conduit 38 is provided with two series of diametricallyopposite radial outlet holes 39.

In particular, ejection conduit 38 is inclined towards outlet portion 26of the relative duct 25 and therefore towards filter layers 15 and 16.

In addition, ejection conduit 38 extends from the same lateral wall 30of the relative inlet portion 27 as heating member 36.

As shown in FIGS. 2 and 3, outlet holes 39 of each ejection conduit 38preferably lie on a common plane extending transversally to the relativeairflow F and defining an acute angle with wall 11 and therefore withfilter layers 15 and 1, parallel to such wall 11.

The particular arrangement of each ejection conduit 38 within therelative duct 25 is aimed at increasing mixing of the sterilizing agentexiting from the outlet holes 39 with the relative airflow F.

Ejection conduit 38 is supplied with the vaporous, gaseous or liquidsterilizing agent by a sterilizing agent reservoir not shown and knownas such.

Each heating member 36 and the corresponding election conduit 38 aredisposed downstream of the relative blower outlet. 23 and upstream offilter layers 15, 16 with respect to the relative airflow F.

Furthermore, each heating member 36 and the corresponding electionconduit 38 are arranged adjacent to one another. In particular, eachejection conduit 38 is disposed downstream of the corresponding heatingmember 36 with respect to the relative airflow F.

With reference to FIG. 3, each duct 25 is also internally provided witha deflector element 40 extending transversally to the relative airflow Fand adapted to disrupt the latter in order to create a turbulentmovement, of the air.

In particular, each deflector element 40 is arranged upstream of therelative heating member 36 and immediately downstream of the relativeblower outlet 23.

Each deflector element 40 projects from one of lateral walls 30 of theinlet portion 27 of the relative duct 25.

In use, during normal working operation, blowers 22 aspirate air fromuntreated environment 2 and generate respective airflows F towards theclean/sterile environment 3. Pre-filters 24 filter out larger-sizedcontaminations from the air directed towards the inside of blowers 22.

The air exit blowers 22 at respective blower outlets 23 and progressesalong respective ducts 25. The airflows F enter respective chambers 20of hollow bodies 18 through volute-like outlet portions 26 of respectiveducts 25.

The use of volute-like outlet portions 26 of ducts 25 along with theparticular arrangement of such outlet portions 26 at opposite sides ofchamber 20 with facing and staggered main outlet openings 31 produce aturbulence in the air within chamber 20. In practice, the air exitingfrom one of main outlet openings 31 flows against the air exiting fromthe other main outlet opening 31 increasing turbulence and mixing of theairflows F. The air then passes thereby through filter layers 15 and 16.

During passage through these filter layers 15, 16, contaminations notfiltered out by pre-filter 24 are removed from the air flowing towardsair outlet 5. Thus, cleaned/sterilized air exits from filter unit 1 andenters clean/sterile environment 3.

When unit 1 needs to be sterilized during a sterilization cycle, thefunction of the unit 1 is essentially identical to what is explainedabove. Additionally to the activation of blowers 22, also respectiveheating members 36 and respective ejection conduits 38 are activated. Inparticular, each heating member 36 heats the relative airflow, whileeach ejection conduit 38 receives the vaporous, gaseous or liquidsterilizing agent from the sterilizing agent reservoir and injects itthrough outlet holes 39 into heated air moving through the relative duct25.

In particular, the sterilizing agent is injected in the ducts 25transversally to the respective airflows F; this together with theturbulence of the air flowing in chamber 20 through the volute-likeoutlet, portions 26 produce a very deep mixing of the sterilizing agentwith the heated air.

The mixture of air and sterilizing agent exits from each duct 25 throughthe opposite main and auxiliary outlet openings 31, 35, thereby reachingany corner of filter layers 15 and 16.

Thus, overall, the airflows F directed through filter layers 15, 16contain a desired quantity of sterilizing agent which is activated byadjusting an adequate temperature of the air in such airflows by theheating members 36. The active sterilizing agent deactivates anddecompose the contaminations leaving behind water and decompositionproducts.

At the end of the sterilization cycle election conduits 38 aredeactivated. Heating members 36 are further maintained in an activecondition until Filter layers 15, 16 are dried out.

Finally, blowers 22 are activated to blow the decomposition products outof the unit alternatively, blowers 22 may be activated to work in asuction mode so as to remove the decomposition products from filterlayers 15, 16 by suction.

The advantages of air filter unit 1 according to the present inventionwill be clear from the foregoing description.

In particular, air filter unit 1 presents, with respect to the knownsolutions previously described and discussed, an increased mixing effectand behavior of the sterilizing agent in the airflows due to:

-   -   use of the volute-like outlet portion 26, which increases        turbulence of the mixture formed by the air and the sterilizing        agent;    -   injection of the sterilizing agent transversally into the        airflows;    -   arrangement of the main outlet openings 31 of the two ducts 25        lying on respective planes transversal to filter layers 15, 16;    -   arrangement of the volute-like outlet portions 26 of the two        ducts 25 at spaced locations within, the chamber 20 and with        their main outlet openings 31 facing an intermediate plane P        there between so as to further increase turbulence of the air;        and    -   use of deflector elements 40 to disrupt the respective airflows        F at the entry within ducts 25, thereby increasing turbulence of        air moving towards the filter layers 15, 16.

In addition, having the outlet portions 26 of the ducts 25 provided withauxiliary outlet openings 35 at opposite locations with respect to therespective main outlet openings 31 allows the mixture of air andsterilizing agent to reach the corners of the box-like structure 10 ofthe filter assembly 6.

The increased mixing effect between the air and the sterilizing agentleads to a more homogeneous distribution of the sterilizing agent withinany part of the filter assembly 6 and in particular of the filter layers15, 16.

Plus, the improved mixing effect between the air and the sterilizingagent allows to reduce the time needed to obtain the desiredsterilization effect of the filter unit 1.

Clearly, changes may be made to air filter unit 1 as described hereinwithout, however, departing from the scope of protection as defined inthe accompanying claims.

In particular, filter assembly 6 may comprise one single filter layer ormore than two filter layers.

Moreover, each pre-filter 24 may be interposed between the respectiveblower 22 and the respective duct 25.

Furthermore, air filter unit 1 may comprise one single blower 22connected to the filter assembly 6 through two ducts 25 and thereforegenerating two airflows F along such ducts 25.

Finally, air filter unit can be realized by comprising one singleheating member 36 adapted to heat both airflows F.

1. An air filter unit for removing contaminations from air, comprising:an airflow generating device configured to generate and direct at leastone airflow from an air inlet to an air outlet; a filter disposedbetween the air inlet and the air outlet and including at least onefilter layer for removing contaminations from the at least one airflow;a heater disposed upstream of the filter and configured to heat the atleast one airflow directed towards the filter; an ejection devicedisposed upstream of the filter and configured to inject a vaporized,gaseous, or liquid sterilizing agent into the at least one airflowdirected towards the filter; and a duct interposed between the air inletand the filter and configured to feed the at least one airflow to thefilter; wherein the duct includes a volute-like outlet portion forconveying the at least one airflow to the filter, and wherein theejection device is arranged in the duct.
 2. The unit according to claim1, wherein the ejection device is configured to inject the sterilizingagent transversally to the at least one airflow.
 3. The unit accordingto claim 1, wherein the ejection device includes an ejection conduitprojecting transversally from a lateral wall within the duct.
 4. Theunit according to claim 3, wherein the ejection conduit is inclinedtowards the filter.
 5. The unit according to claim 3, wherein theejection conduit includes at least one radial outlet hole having an axistransversal to the at least one airflow.
 6. The unit according to claim1, wherein the heater is arranged in the duct.
 7. The unit according toclaim 1, wherein the heater and the ejection device are adjacent to oneanother.
 8. The unit according to claim 1, wherein the volute-likeoutlet portion of the duct opens into a chamber located adjacent to, andupstream of, the at least one filter layer with respect to the at leastone airflow, and wherein the volute-like outlet portion defines a mainoutlet opening lying on a plane transversal to the at least one filterlayer.
 9. The unit according to claim 8, wherein the plane on which themain outlet opening lies is slanted with respect to the at least onefilter layer and defines an acute angle with the at least one filterlayer.
 10. The unit according to claim 8, wherein the volute-like outletportion of the duct includes an auxiliary outlet opening arranged withinthe chamber and opposite to the main outlet opening.
 11. The unitaccording to claim 10, wherein the main outlet opening of thevolute-like outlet portion of the duct is larger than the auxiliaryoutlet opening.
 12. The unit according to claim 1, further comprising adeflector element arranged inside the duct and extending transversallyto the at least one airflow, the deflector element configured to disruptthe at least one airflow.
 13. The unit according to claim 12, whereinthe deflector element is arranged upstream of the heater and theejection device.
 14. The unit according to claim 1, wherein the at leastone filter layer includes two filter layers, wherein a first filterlayer is disposed the airflow generating device and the air outlet, anda second filter layer is disposed between the first filter layer and theair outlet.
 15. The unit according to claim 8, wherein the air inletincludes two air inlets, and the duct includes two ducts interposedbetween the respective air inlets and the respective filters andconfigured to feed two airflows to the filter, and wherein thevolute-like portions of the respective ducts are arranged at oppositesides of the chamber.
 16. The unit according to claim 15, wherein themain outlet openings of said the respective ducts face respectivestaggered portions of an intermediate plane extending between therespective ducts and orthogonal to the filter.